Chrysler Repair: 1998 Concord A/C, radiator fans, conventional control

Question
My son has a Concord and the a/c has gone out twice the dealership has charged him 400.00 the first time. He is in the service and the $ is hard for him to come up with so I am trying to help diagnose the problem. a/c blows but warm air. freon has been checked and it is good. what would the problem be? and how to fix?
Thanks
Kurt  

Answer
Hi Kurt,
Is the unit a conventional control panel or is it one with a digital display on which you select a temperature? The latter type of unit has a fairly complete self diagnostic system, while the former has a rudimentary system. So let me know that, please.
Then the another question is does the compressor clutch engage when you ask for cooling to occur? You can do this at park, open the hood, and see what happens at the compressor when a helper initiates a request for cooling. The clutch at the compressor should click and the compressor should then be connected, and also the radiator fans should begin to blow. Let me know if that happens or not.
Also, how long ago was the last time the dealer (or anyone else) was paid to work on the A/C?  Might it have a warranty period that is still in effect?
So let me know the answer to those questions, and we'll proceed from there.
Roland